Baby steps towards an odeon-like animation system. First victim: Drawer.

sky/sdk/lib/painting/box_painter.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'dart:sky' show Point, Offset, Size, Rect, Color, Paint, Path;
 
+import '../base/lerp.dart';
 import 'shadows.dart';
 import 'package:sky/mojo/net/image_cache.dart' as image_cache;
 
 class BorderSide {
   const BorderSide({
     this.color: const Color(0xFF000000),
     this.width: 1.0
   });
   final Color color;
   final double width;
@@ skipping 46 matching lines @@
     this.blur
   });
 
   final Color color;
   final Offset offset;
   final double blur;
 
   String toString() => 'BoxShadow($color, $offset, $blur)';
 }
 
+BoxShadow lerpBoxShadow(BoxShadow a, BoxShadow b, double t) {
+  return new BoxShadow(
+      color: lerpColor(a.color, b.color, t),
+      offset: lerpOffset(a.offset, b.offset, t),
+      blur: lerpNum(a.blur, b.blur, t));
+}
+
 abstract class Gradient {
   sky.Shader createShader();
 }
 
 class LinearGradient extends Gradient {
   LinearGradient({
     this.endPoints,
     this.colors,
     this.colorStops,
     this.tileMode: sky.TileMode.clamp
@@ skipping 288 matching lines @@
     path.close();
     canvas.drawPath(path, paint);
   }
 
   void paint(sky.Canvas canvas, Rect rect) {
     _paintBackgroundColor(canvas, rect);
     _paintBackgroundImage(canvas, rect);
     _paintBorder(canvas, rect);
   }
 }